Along with the vigorous development of hydropower resources

many super high arch dams are constructing in Southwest region of China. The stability of these arch dams is a key and important problem in the process of design and construction. As for those arch dams constructed in high ground stress valley

foundation excavation may lead to geostress release and unloading of rock mass

and then causes shallow stability problem

which has few successful example for us to learn how to design and reinforce foundation for super high arch dam under these geo-condition. To this problem

unsuitable concept may bring about wrong calculation or numerical simulation

and then lead error to occur during design process. A detailed discussion is conducted focusing on the characters and mechanism of shallow unloading of excavated foundation surface of super high arch dam. Based on the Xiaowan Arch Dam

the calculation method of unbalance force of abutment and surface factor of safety of dam interface are proposed. By employing maximum-minimum principle

the stability of foundation interface of Xiaowan Arch Dam was analyzed and evaluated for supervising the design. The analysis results show that the proposed method is effective to supervise design for those super high arch dams similar to Xiaowan Arch Dam.